Quick reply, I'm not getting into the weeds this late.
Drive shaft is almost 100% requiring replacement. Biggest determining factor with diameter is engine power and your right foot. However, it's almost guranteed that you will need a different length and transmission yoke to match your transmission and where its tailshaft is located.
Rear end will depend completely on your foot. Many Rangers with the 4 cylinders came with a 7.5 axle right into the 2000s. Some may have gotten a 8.8 depending on options. Many 7.5s have survived behind a 5.0L with appropriate application of the skinny pedal. Same for the Ranger's 28 spline 8.8. If you plan to be matting the skinny pedal a lot consider upgrade to a 31 spline Explorer 8.8".
Your stock 2.3L fuel system is setup for 35-45 PSI to support EFI. This is going to be way too much for a carburetor, you will need to run a pressure regulator to drop fuel pressure to ~5 PSI, maybe lower.
I'm not sure about the validity of the information you've heard on the M5OD-R2 as it regards a 2wd. It's likely right for a 4wd, assuming that the engine placement doesn't need it sitting further back. Personally, I'd forget about counting on stock transmission mount placement, let the engineplacement determine it's position. If you want a 2wd street truck build consider other transmissions. The M5OD works fine, but there are better shifting options for a street truck. They may take more work, but the reward in shifting and gearing is likely worth the effort. Your choice, but I still say let the engine position determine transmission location, not the other way around.
Your engine choice is not a good one. For the most part a 5.0L roller block is a 5.0L roller block. I don;t think that those heads are very desirable, you would be better served with a set of 96-97 Explorer GT-40 heads. Second best factory production head ever installed. Best is the later GT-40P, but those have an odd spark plug angle that hakes headers and plug wires difficult. Even the mustang guys wanted the GT-40 heads before aftermarket aluminum got so cheap. Stock mustang cam is a nice small bump over the Explorer cam, don't know how it compares the the GM cam. The biggest problem with the GM is litterally the biggest problem. They are big compared to a Mustang or Ranger, they have a big engine bay. The acessory package for that will not be a good fit in the Ranger. You want the Fox Mustang, or even better the Explorer accessory drive for best fitment. Explorer was the smallest and best fit in a Ranger bay. There's a reason we recommend Explorers as donors for all Ranger 5.0L swaps.
Springs, if you are a regular cab consider getting a set of Extended cab springs. There's about hundred lbs difference between the original V6 drivetrains and the V8 drivetrain. The extended cab springs should do the job nicely. Either way a new set of springs is naturally going to raise the truck some over the sagged 30 year old units.
(Ok, maybe that wasn't such a quick reply. Still all the detail I'm going ot get into tonight.)